1. Field of the Invention
This invention relates to a method for making parts in which two or more parts have shaped surfaces that must bear a precision relationship. More particularly this invention relates to a method for making parts having both trochoidal and circular surfaces that must be positioned in precision relationship to each other. Such machines are useful in speed change devices and other units having a plurality of shaped surfaces which must have a near perfect eccentricity between all of the shaped surfaces.
2. Description of the Related Art
Speed change devices having both hypotrochoidal and epitrochoidal surfaces that must bear predetermined precision positions in relation to each other and to circular bearing races are described in U.S. Pat. Nos. 4,584,904 to Distin and Shaffer and No. 4,643,047 to Distin. The speed change devices described in those patents make use of rollers positioned between adjacent epitrochoidal and hypotrochoidal bearing races to reduce friction and backlash. Grinding machines for making such parts typically are capable of grinding only one surface without making a new set-up. In speed change devices made by such a method it is difficult or impossible to maintain the degree of concentricity necessary for optimum operation. U.S. Pat. No. 4,186,529 to Huffman describes a method for grinding cutting edges and clearance surfaces in which a series of grinding operations are performed by the same grinding wheel while the tool remains in the same work holder. However, the machine described in that patent cannot be used to grind continuous surfaces and does not make use of two continuously rotating tables supporting the part to be machined as in applicant's method.